Warm "hello" for the matscan. Removing garbage when shutting down a listener thread

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>net.rubeta</groupId>
     <artifactId>LegacyPing</artifactId>
-    <version>1.2</version>
+    <version>2.2</version>
     <packaging>jar</packaging>
 
     <name>LegacyPing</name>

src/main/java/net/rubeta/legacyping/CrutchBukkitMirrorThread.java

@@ -0,0 +1,106 @@
+package net.rubeta.legacyping;
+
+import net.minecraft.network.packets.Packet;
+import net.minecraft.network.packets.Packet255KickDisconnect;
+import org.bukkit.craftbukkit.CraftServer;
+import org.bukkit.craftbukkit.event.CraftEventFactory;
+import org.bukkit.event.server.ServerListPingEvent;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.EOFException;
+import java.io.IOException;
+import java.net.*;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class CrutchBukkitMirrorThread extends Thread {
+
+    private final AtomicBoolean working = new AtomicBoolean(false);
+    private final Logger logger;
+    private ServerSocket serverSocket;
+    private final InetAddress address;
+    private final LegacyPing plugin;
+
+    public CrutchBukkitMirrorThread(final LegacyPing plugin) {
+        this.plugin = plugin;
+        this.logger = Logger.getLogger("mirror:25565");
+
+        try {
+            this.address = InetAddress.getByName("0.0.0.0");
+        } catch (UnknownHostException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    @Override
+    public void run() {
+        this.working.set(true);
+        while (this.working.get()) {
+            try {
+                this.serverSocket = new ServerSocket(25565, 10, address);
+                this.serverSocket.setSoTimeout((int) TimeUnit.SECONDS.toMillis(10L));
+                this.serverSocket.setPerformancePreferences(0, 2, 1);
+            } catch (IOException e) {
+                this.logger.log(Level.WARNING, "Failed to start ServerSocket", e);
+                this.pause();
+                continue;
+            }
+
+            while (!this.serverSocket.isClosed()) {
+                if (!this.working.get()) {
+                    break;
+                }
+
+                InetAddress address = null;
+                try (final Socket socket = this.serverSocket.accept()) {
+                    final DataInputStream inputStream = new DataInputStream(socket.getInputStream());
+                    final DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
+                    address = socket.getInetAddress();
+                    socket.setTrafficClass(SocketOptions.TCP_NODELAY & SocketOptions.IP_TOS);
+                    inputStream.readInt(); // Packet length
+                    Packet packet = Packet.readPacket(inputStream);
+                    if (packet != null && packet.getPacketId() == 254) {
+                        CraftServer server = (CraftServer) this.plugin.getServer();
+                        ServerListPingEvent pingEvent = CraftEventFactory.callServerListPingEvent(
+                                server, address, server.getServer().motd,
+                                server.getOnlinePlayers().length, server.getMaxPlayers()
+                        );
+                        String s = pingEvent.getMotd() + "\u0000" + server.getOnlinePlayers().length + "\u0000" + pingEvent.getMaxPlayers();
+                        Packet255KickDisconnect response = new Packet255KickDisconnect(s);
+                        outputStream.writeInt(s.length() + 1);
+                        outputStream.writeByte(255);
+                        response.writePacketData(outputStream);
+                    }
+                } catch (SocketTimeoutException | EOFException ignore) {
+                } catch (Exception ex) {
+                    this.logger.warning("An exception occurred while communicating with " + address);
+                    this.logger.log(Level.WARNING, "Exception in " + this.getName(), ex);
+                }
+            }
+        }
+    }
+
+
+    public void shutdown() {
+        this.working.set(false);
+        try {
+            this.serverSocket.close();
+        } catch (IOException ignore) {
+        }
+    }
+
+
+    void pause() {
+        this.pause(TimeUnit.SECONDS.toMillis(30L));
+    }
+
+    void pause(long millis) {
+        try {
+            Thread.sleep(millis);
+        } catch (InterruptedException ignored) {
+        }
+    }
+}

src/main/java/net/rubeta/legacyping/LegacyPing.java

@@ -1,5 +1,8 @@
 package net.rubeta.legacyping;
 
+import org.bukkit.ChatColor;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
 import org.bukkit.configuration.file.FileConfiguration;
 import org.bukkit.plugin.java.JavaPlugin;
 
@@ -10,25 +13,54 @@ import java.util.logging.Level;
 
 public final class LegacyPing extends JavaPlugin {
     private final List<ServerThread> threads = new ArrayList<>();
+    private CrutchBukkitMirrorThread mirror = null;
 
     @Override
     public void onEnable() {
         this.saveDefaultConfig();
+        this.startThreads();
+    }
+
+    private void startThreads() {
         final FileConfiguration config = this.getConfig();
         final String host = config.getString("host", "0.0.0.0");
         final List<Integer> ports = config.getIntegerList("port");
+        final String version = config.getString("displayedVersion", "b1.7.3");
+        final int protocol = config.getInt("displayedProtocol", 14);
         for (int port : ports) {
             try {
-                this.threads.add(new ServerThread(this.getServer(), host, port));
+                this.threads.add(new ServerThread(this, host, port, version, protocol));
             } catch (IOException e) {
                 this.getLogger().log(Level.WARNING, "Failed to create ServerSocket", e);
             }
         }
+        if (config.getBoolean("enableMirrorPort", false)) {
+            this.mirror = new CrutchBukkitMirrorThread(this);
+            this.mirror.start();
+        }
         this.threads.forEach(Thread::start);
     }
 
     @Override
     public void onDisable() {
+        if (this.mirror != null) {
+            this.mirror.shutdown();
+        }
         this.threads.forEach(ServerThread::shutdown);
     }
+
+    @Override
+    public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
+        if (!sender.isOp()) {
+            return true;
+        }
+        if (this.mirror != null) {
+            this.mirror.shutdown();
+        }
+        this.threads.forEach(ServerThread::shutdown);
+        this.threads.clear();
+        this.startThreads();
+        sender.sendMessage(ChatColor.GOLD + "Restarted");
+        return true;
+    }
 }

src/main/java/net/rubeta/legacyping/ServerThread.java

@@ -5,67 +5,127 @@ import org.bukkit.craftbukkit.CraftServer;
 
 import java.io.*;
 import java.net.*;
+import java.nio.charset.StandardCharsets;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 public class ServerThread extends Thread {
 
     private static final String MODERN_RESPONSE =
-            "{\"version\": {\"name\": \"b1.7.3\",\"protocol\": -17}," +
-                    "\"players\": {\"max\": %max%,\"online\": %now%,\"sample\": []}," +
-                    "\"description\": {\"text\": \"%motd%\"},\"enforcesSecureChat\": false}";
-    private final ServerSocket serverSocket;
+            "{\"version\": {\"name\": \"%version%\",\"protocol\": %protocol%}," +
+                    "\"players\": {\"max\": %max%,\"online\": %now%}," +
+                    "\"description\": {\"text\": \"%motd%\"}," +
+                    "\"enforcesSecureChat\": false,\"previewsChat\": false}";
+    private static final String DISCONNECT_REASON = "[\"\",{\"text\":\"This is b1.7.3 server. Visit \"}," +
+            "{\"text\":\"https://rubeta.net\",\"underlined\":true},{\"text\":\" for more information.\"}]";
+    private static final String SLOWSTACK_ID = "slowstack.tv";
+    private static final String MATSCAN_ID = "matscan";
     private final AtomicBoolean working = new AtomicBoolean(false);
     private final Server minecraftServer;
+    private final String version;
+    private final int protocol;
+    private final InetAddress address;
+    private final int port;
+    private final Logger logger;
+    private ServerSocket serverSocket;
 
-    public ServerThread(final Server server, final String host, int port) throws IOException {
-        this.minecraftServer = server;
+    public ServerThread(final LegacyPing plugin, final String host, int port, String version, int protocol) throws IOException {
+        this.minecraftServer = plugin.getServer();
+        this.logger = plugin.getLogger();
         this.setName("LegacyPing thread listening " + host + ":" + port);
-        final InetAddress address = InetAddress.getByName(host);
-        this.serverSocket = new ServerSocket(port, 10, address);
-        this.serverSocket.setSoTimeout((int) TimeUnit.SECONDS.toMillis(10L));
-        this.serverSocket.setPerformancePreferences(0, 2, 1);
+        this.version = version;
+        this.protocol = protocol;
+        this.address = InetAddress.getByName(host);
+        this.port = port;
     }
 
     public ServerThread(final String host, int port) throws IOException {
         this.minecraftServer = null;
         this.setName("LegacyPing thread listening " + host + ":" + port);
-        final InetAddress address = InetAddress.getByName(host);
-        this.serverSocket = new ServerSocket(port, 10, address);
-        this.serverSocket.setSoTimeout((int) TimeUnit.SECONDS.toMillis(10L));
-        this.serverSocket.setPerformancePreferences(0, 2, 1);
+        this.logger = Logger.getLogger(host + ":" + port);
+        this.version = "dummy";
+        this.protocol = 0;
+        this.address = InetAddress.getByName(host);
+        this.port = port;
     }
 
     public static void main(String[] args) throws IOException {
-        new ServerThread("", 25565).start();
+        new ServerThread("", 25569).start();
     }
 
+    @SuppressWarnings("unused")
     @Override
     public void run() {
         this.working.set(true);
-        while (this.working.get() && !this.serverSocket.isClosed()) {
+        while (this.working.get()) {
             try {
-                final Socket socket = this.serverSocket.accept();
-                socket.setTrafficClass(SocketOptions.TCP_NODELAY & SocketOptions.IP_TOS);
-                System.out.println("[LegacyPing] Got new ping from " + socket.getRemoteSocketAddress());
-                final InputStream inputStream = socket.getInputStream();
-                final OutputStream outputStream = socket.getOutputStream();
-                final int firstByte = inputStream.read();
-                switch (firstByte) {
-                    case 0:
-                        this.responseForRuBetaModdedClient(outputStream);
-                        break;
-                    case 254:
-                        this.responseForLegacyPing(outputStream);
-                        break;
-                    default:
-                        this.responseForModernPing(outputStream);
+                this.serverSocket = new ServerSocket(port, 10, address);
+                this.serverSocket.setSoTimeout((int) TimeUnit.SECONDS.toMillis(10L));
+                this.serverSocket.setPerformancePreferences(0, 2, 1);
+            } catch (IOException e) {
+                this.logger.log(Level.WARNING, "Failed to start ServerSocket", e);
+                this.pause();
+                continue;
+            }
+
+            while (!this.serverSocket.isClosed()) {
+                if (!this.working.get()) {
+                    break;
+                }
+                InetAddress address = null;
+                try (final Socket socket = this.serverSocket.accept()) {
+                    final DataInputStream inputStream = new DataInputStream(socket.getInputStream());
+                    final DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
+                    address = socket.getInetAddress();
+                    socket.setTrafficClass(SocketOptions.TCP_NODELAY & SocketOptions.IP_TOS);
+
+                    final int packetLength = inputStream.readByte() | inputStream.readByte() << 1; // idk why it doesn't a VarInt
+                    final int protocolVersion = this.readVarInt(inputStream);
+                    final String hostname = this.readUtf(inputStream);
+                    final int port = inputStream.readShort();
+                    final int status = this.readVarInt(inputStream);
+                    this.logger.info("Ping from " + socket.getRemoteSocketAddress() + " to " + hostname + ":" + port);
+                    if (status != 2) {
+                        if (hostname.equalsIgnoreCase(SLOWSTACK_ID)) {
+                            this.responseForModernPing(outputStream, MODERN_RESPONSE.replace(
+                                    "%motd%", "%motd% \nHello, slowstack.tv!"
+                            ));
+                        } else if (hostname.equalsIgnoreCase(MATSCAN_ID)) {
+                            this.responseForModernPing(outputStream, MODERN_RESPONSE
+                                    .replace("%motd%", "%motd% \nHello, matscan!")
+                                    .replace("%version%", "⚠ Error")
+                            );
+                        } else {
+                            this.responseForModernPing(outputStream, MODERN_RESPONSE);
+                        }
+                    } else {
+                        this.responseForModernPing(outputStream, DISCONNECT_REASON);
+                        socket.close();
+                        continue;
+                    }
+                    outputStream.flush();
+
+                    this.pause(50L);
+                    if (socket.isClosed() || !socket.isConnected() || inputStream.available() == 0) {
+                        continue;
+                    }
+                    inputStream.readShort(); // legacy data
+                    this.pause(50L);
+                    if (socket.isClosed() || !socket.isConnected() || inputStream.available() == 0) {
+                        continue;
+                    }
+                    this.writeVarInt(outputStream, this.readVarInt(inputStream)); // Packet length  (9)
+                    this.writeVarInt(outputStream, this.readVarInt(inputStream)); // Packet id      (1)
+                    outputStream.writeLong(inputStream.readLong()); // timestamp
+                } catch (SocketTimeoutException | EOFException ignore) {
+                } catch (Exception ex) {
+                    if (this.working.get()) {
+                        this.logger.warning("An exception occurred while communicating with " + address);
+                        this.logger.log(Level.WARNING, "Exception in " + this.getName(), ex);
+                    }
                 }
-                outputStream.flush();
-                socket.close();
-            } catch (SocketTimeoutException ignore) {
-            } catch (IOException ex) {
-                System.out.println("Exception caught: " + ex);
             }
         }
     }
@@ -78,44 +138,31 @@ public class ServerThread extends Thread {
         }
     }
 
-    private void responseForRuBetaModdedClient(final OutputStream outputStream) throws IOException {
-        final ByteArrayOutputStream result = new ByteArrayOutputStream();
-        final DataOutputStream dos = new DataOutputStream(result);
-        dos.write(255); // Packet 0xFF (PacketDisconnect)
-        final String response = this.getMotd() + '\u0000' + this.getOnlinePlayers() + '\u0000' + this.getMaxPlayers();
-        dos.writeShort(response.length());
-        for (char c : response.toCharArray()) {
-            dos.writeChar(c);
-        }
-        // Packet data end
-        final DataOutputStream clientOutput = new DataOutputStream(outputStream);
-        clientOutput.writeInt(result.size());
-        clientOutput.write(result.toByteArray());
+    void pause() {
+        this.pause(TimeUnit.SECONDS.toMillis(30L));
     }
 
-    @SuppressWarnings("UnnecessaryUnicodeEscape")
-    private void responseForLegacyPing(final OutputStream outputStream) throws IOException {
-        final DataOutputStream clientOutput = new DataOutputStream(outputStream);
-        clientOutput.write(255);
-        final String response = this.getMotd() + '\u00a7' + this.getOnlinePlayers() + '\u00a7' + this.getMaxPlayers();
-        clientOutput.writeShort(response.length());
-        for (char c : response.toCharArray()) {
-            clientOutput.writeChar(c);
+    void pause(long millis) {
+        try {
+            Thread.sleep(millis);
+        } catch (InterruptedException ignored) {
         }
-        // Packet data end
     }
 
-    private void responseForModernPing(final OutputStream outputStream) throws IOException {
-        final String responseJson = MODERN_RESPONSE.replace("%max%", String.valueOf(this.getMaxPlayers()))
+    private void responseForModernPing(final DataOutputStream outputStream, String response) throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        DataOutputStream dos = new DataOutputStream(baos);
+        final String responseJson = response
+                .replace("%version%", String.valueOf(this.version))
+                .replace("%protocol%", String.valueOf(this.protocol))
+                .replace("%max%", String.valueOf(this.getMaxPlayers()))
                 .replace("%now%", String.valueOf(this.getOnlinePlayers()))
                 .replace("%motd%", this.getMotd());
-        byte[] bytes = responseJson.getBytes();
-        final DataOutputStream clientOutput = new DataOutputStream(outputStream);
-        this.writeVarInt(clientOutput, bytes.length + 3);
-        this.writeVarInt(clientOutput, 0);
-        this.writeVarInt(clientOutput, bytes.length);
-        clientOutput.write(bytes);
-        // Packet data end
+        this.writeVarInt(dos, 0);
+        this.writeUtf(dos, responseJson);
+        dos.close();
+        this.writeVarInt(outputStream, baos.size());
+        outputStream.write(baos.toByteArray());
     }
 
     private String getMotd() {
@@ -130,14 +177,46 @@ public class ServerThread extends Thread {
         return this.minecraftServer == null ? 37 : this.minecraftServer.getMaxPlayers();
     }
 
+    public int readVarInt(DataInputStream in) {
+        int i = 0;
+        int j = 0;
+        try {
+            byte b0;
+            do {
+                b0 = in.readByte();
+                i |= (b0 & 127) << j++ * 7;
+                if (j > 5) {
+                    throw new RuntimeException("VarInt too big");
+                }
+            } while ((b0 & 128) == 128);
+        } catch (Exception ignore) {
+            return 0;
+        }
+        return i;
+    }
+
     private void writeVarInt(DataOutputStream out, int paramInt) throws IOException {
-        while (true) {
-            if ((paramInt & 0xFFFFFF80) == 0) {
-                out.writeByte(paramInt);
-                return;
-            }
-            out.writeByte(paramInt & 0x7F | 0x80);
+        while ((paramInt & 0xffffff80) != 0) {
+            out.writeByte(paramInt & 0x7f | 0x80);
             paramInt >>>= 7;
         }
+        out.writeByte(paramInt);
+    }
+
+    @SuppressWarnings("ResultOfMethodCallIgnored")
+    private String readUtf(DataInputStream in) throws IOException {
+        int length = this.readVarInt(in);
+        byte[] data = new byte[length];
+        in.read(data);
+        return new String(data, StandardCharsets.UTF_8);
+    }
+
+    private void writeUtf(DataOutputStream out, String string) throws IOException {
+        byte[] data = string.getBytes(StandardCharsets.UTF_8);
+        if (data.length > 32767) {
+            throw new RuntimeException("String too big (was " + data.length + " bytes encoded, max 32767");
+        }
+        this.writeVarInt(out, data.length);
+        out.write(data);
     }
 }

src/main/resources/config.yml

@@ -2,3 +2,5 @@ host: '0.0.0.0'
 port:
   - 25566
   - 25567
+displayedVersion: 'b1.7.3'
+displayedProtocol: 17

src/main/resources/plugin.yml

@@ -1,3 +1,10 @@
 name: LegacyPing
 version: '${project.version}'
 main: net.rubeta.legacyping.LegacyPing
+commands:
+  legacyping:
+    permission: legacyping.command.legacyping
+
+permissions:
+  legacyping.command.legacyping:
+    default: op